Short-term probiotic supplementation enhances cellular immune function in healthy elderly: systematic review and meta-analysis of controlled studies

Abstract Immune function declines with advancing age. Probiotic supplementation has been proposed to slow or reverse these age-related changes. The primary objective of this study was to evaluate the effect of probiotic supplementation on cellular innate immune activity in healthy elderly subjects. We hypothesized that probiotic supplementation would enhance immune function. We performed a systematic review and meta-analysis of controlled trials that reported polymorphonuclear (PMN) cell phagocytic capacity or natural killer (NK) cell tumoricidal activity following short-term probiotic supplementation in the elderly. Effect size was reported as the standardized mean difference (SMD) between probiotic and control groups, where values of 0.2, 0.5, 0.8, and 1.0 corresponded to small, medium, large, and very large effect sizes, respectively. A total of 17 prospective controlled studies (18 comparisons) of 733 subjects were included. Probiotic supplementation duration ranged from 3 to 12 weeks. Probiotic supplementation increased PMN phagocytic capacity (SMD = 1.37, 95% confidence interval: 0.86 to 1.88, P P